1. Field of the Invention
The present invention relates to a surface texture measuring instrument and a method of adjusting an attitude of a work in the surface texture measuring instrument for a measurement of a surface texture of the work such as a roughness, waviness, contour, and the like, and more particularly relates to a method of correcting the attitude thereof by adjusting a direction of a feature region thereof such as a V groove or an accurate groove and a measuring direction of a detector before the measurement.
2. Description of the Related Art
Conventionally, a form measuring instrument is known which performs roughness measurement, profile measurement, and the like of a work having a feature region such as a V groove or an accurate groove in a fixed direction. In this form measuring instrument, in a case where, for instance, the cross-sectional shape of a V groove or a pitch between grooves of a plurality of rows of V grooves in a work is measured, the work is mounted on a stage such that the direction in which the V groove extends is aligned with a Y-axis direction, a detector is driven in a direction perpendicular to the direction in which the V groove extends (X-axis direction), and stylus type measuring instrument is performed on the basis of an output of the detector.
With the above-described form measuring instrument, however, there has been no appropriate method for allowing the direction in which, for example, the V groove extends to be accurately aligned with the Y-axis direction. Therefore, in the related art, measurement has been carried out not in a direction accurately perpendicular to the direction in which the V groove or an accurate groove in the work extends but in a direction which is angularly offset though at a very small angle. Consequently, the cross-sectional shape of the groove or the pitch between grooves showed results which are different from actual ones. In fact, the measurement results exhibited values slightly smaller than those of a real groove shape or pitch between grooves.
To overcome these drawbacks, it has been practiced to conduct measurement while changing the attitude of the work by very small degrees so as to obtain results close to real values. However, since this method is very troublesome and makes it necessary to perform trial measurement a number of times, so that in the case of a probe-type measuring machine there have been cases where the work is damaged in a case where material of the work is soft.
It is an object of the invention to provide a surface texture measuring instrument capable of adjusting the relative attitude of a work mounted on a stage with respect to a coordinate system of the surface texture measuring instrument, capable of easily and precisely adjusting the mounted attitude with respect to the coordinate system even in the case of a work having a feature region in a fixed direction, and capable of reducing the time required for initial setup of measurement and of preventing the occurrence of damage to the work.
It is a further object of the invention to provide a method of adjusting the relative attitude of the work in the surface texture measuring instrument.
To attain the above object, the method of adjusting the relative attitude of the work in the surface texture measuring instrument in accordance with the invention has the following steps.
In first aspect of the invention, there is provided a method of adjusting the relative attitude of the work in the surface texture measuring instrument including: a stage for mounting thereon the work having a feature region along a fixed direction of a surface thereof such that the fixed direction becomes substantially aligned with a direction of a Y axis; a detector for detecting relative displacement of a direction of a Z axis substantially perpendicular to a surface of the work and perpendicular to the Y axis; a Y-axis moving unit for relatively moving the detector and the work in the Y-axis direction; an X-axis moving means for relatively moving the detector and the work in a direction of an X axis perpendicular to the Y axis and the Z axis, respectively, so as to effect measurement; and swivel means for relatively rotating the work and the detector in a X-Y plane including the X axis and the Y axis, so as to measure the surface quality of the work from the relative displacement outputted from the detector, the method characterized by comprising: a measurement step of effecting measurement by relatively positioning the detector with respect to the Y-axis direction and relatively moving the detector along the X-axis direction to obtain data on the feature region; a repeated determination step of repeating the measurement step more than once and storing n (nxe2x89xa72) sets of data on the feature region; a relative-correction-amount calculating step of determining an amount of relative attitude correction of the work with respect to the detector by determining n feature points from n sets of data on the feature region and by determining a feature line connecting the feature points; and an adjustment step of adjusting the relative attitude of the work with respect to the detector on the basis of the amount of relative attitude correction.
According to second aspect of the invention, in the adjustment of the attitude of a work having a feature region such as a V groove or an accurate protrusion along a fixed direction on the surface, the direction of the feature region of the work mounted on a work-attitude adjusting table can be made accurately parallel to the Y axis. Subsequently, if the final measurement is effected in the X-axis direction, it is possible to accurately determine the cross-sectional shape of the V groove or the accurate protrusion. Furthermore, it is possible to accurately determine the distance between grooves in the case of the work having a plurality of grooves or the like.
Accordingly, since the accurate attitude adjustment of the work, which is essential to the precise measurement of the surface quality of the work, can be effected easily and speedily, no damage is caused to the work, and a reduction of the so-called initial setup time for measurement is made possible, thereby making it possible to improve the overall efficiency of the measurement operation and improve the measurement accuracy.
In accordance with second aspect of the invention, the method of adjusting the relative attitude of a work in a surface texture measuring instrument according to claim 1 is characterized by further comprising the step of displaying or printing out the amount of relative attitude correction calculated in the relative-correction-amount calculating step, wherein the attitude adjustment in the adjustment step is manual adjustment which is effected while referring to a result displayed or printed out.
According to the above-described invention, the inclination of the relative attitude of the work is displayed or printed out as an angle or a manipulated variable, and manual adjustment is performed by the operator in accordance with that value, so that accurate operation which is low cost and free of errors becomes possible. In particular, if a micrometer head is used at the operating portion of the attitude adjusting means, precise adjustment ca be made easily, so that more precise attitude adjustment becomes possible. In addition, if a micrometer head capable of digitally displaying the values of the manipulated variables is used, attitude adjustment which is more speedy, reliable, and precise becomes possible.
In accordance with a third aspect of the invention, the method of adjusting the relative attitude of a work in a surface texture measuring instrument according to claim 1 is characterized in that the attitude adjustment in the adjustment step is automatic adjustment based on the calculated amount of relative attitude correction.
According to the above-described invention, since the relative attitude adjustment of the work is automatically effected on the basis of the calculated amount of relative attitude correction, the attitude adjustment of the work as the initial setup of measurement can be performed at high speed, and the burden on the operator is alleviated. Hence, it is possible to improve the overall efficiency of the measurement operation and improve the reliability.
In accordance with a forth aspect of the invention, the method of adjusting the relative attitude of a work in a surface texture measuring instrument according to any one of claims 1 to 3 is characterized in that the adjustment step includes a swiveling adjustment step of adjusting the relative attitude of the work with respect to the detector by relatively rotating the work in the X-Y plane by swivel means.
According to the above-described invention, since the work undergoes relative rotation in the X-Y plane including the X axis and the Y axis to permit its attitude, the direction of the feature region such as the direction of the bottom of a V groove can be easily adjusted parallel to the direction of the Y axis perpendicular to the X axis which is the measuring direction. In addition, the amount of correction in the X-Y plane can be calculated by a trigonometric function and a algebraic calculation, and it is unnecessary to use a special operating processor, so that the calculation can be performed at low cost, accurately, and at high speed.
In accordance with a fifth aspect of the invention, the method of adjusting the relative attitude of a work in a surface texture measuring instrument according to any one of claims 1 to 4 is characterized in that the surface texture measuring instrument further includes tilting means for relatively rotating the work and the detector in a Y-Z plane including the Y axis and the Z axis, and the adjustment step further includes a tilting adjustment step of adjusting the relative attitude of the work with respect to the detector by relatively rotating the work in the Y-Z plane by the tilting means.
According to the above-described invention, since the work undergoes relative rotation in the Y-Z plane including the Y axis and the Z axis to permit its attitude, the direction of the feature region such as the direction of the bottom of a V groove can be easily adjusted parallel to the direction of the Y axis perpendicular to the X axis which is the measuring direction. In addition, the amount of correction in the Y-Z plane can be calculated by a trigonometric function and a algebraic calculation, and it is unnecessary to use a special operating processor, so that the calculation can be performed at low cost, accurately, and at high speed.
In accordance with a sixth aspect of the invention, the method of adjusting the relative attitude of a work in a surface texture measuring instrument according to any one of claims 1 to 5 is characterized in that the relative-correction-amount calculating step further includes a step of determining the n shape feature points from the n sets of data on the feature region and setting coordinate values thereof as coordinate values of the n feature points.
According to the above-described invention, instead of determining a feature point directly from the measurement data on the feature region including noise and the like, the best fit of a design shape corresponding to the shape of the feature region is performed to eliminate errors ascribable to noise and an attitude error, thereby making it possible accurately estimate the shape of the feature region in the measurement portion. Furthermore, if the feature region is accurate, its center position can be used as a feature point, and if the feature region is a combination of straight lines, a point of intersection of straight lines determined by least square method can be used as a feature point. Thus it is possible to use ideal feature points in correspondence with the shape of a special region, so that it becomes possible to perform highly accurate and reliable attitude calculation.
In accordance with a seventh aspect of the invention, the method of adjusting the relative attitude of a work in a surface texture measuring instrument according to any one of claims 1 to 6 is characterized in that in the relative-correction-amount calculating step a least-square straight line determined from the coordinate values of the n feature points is set as the feature line.
According to the above-described invention, since the connection of a plurality of feature points is replaced by a least-square straight line which is set as a feature line, it becomes possible to minimize the error ascribable to noise and a partial processing error in the work. Consequently, it becomes possible to perform highly precise and reliable attitude calculation, and the attitude of the work can be determined accurately, so that the attitude adjustment accuracy improves overall.